1. Field of the Invention
This invention relates to footwear, and in particular to footwear having a "flasher module," i.e., an arrangement for illuminating the shoe in response to movement of the shoe.
2. Discussion of Related Art
Shoes having flasher modules have been commercially available for several years. Generally, such shoes have utilized mercury switches and permanently mounted lithium batteries to provide the flashing effect, but there has been a recent trend to replace at least the mercury switches by safer, less expensive, and less environmentally harmful switching arrangements. Safety, cost, and environmental effects are all significant problems since the most common applications for flasher units of this type are in athletic and children's shoes, which wear out or are outgrown relatively rapidly, and which tend to be subject to greater abuse than other types of shoes. If the electrical units are not exposed during use, they will inevitably become exposed after being discarded, creating a great enough hazard that shoes containing mercury switches have been banned in a number of jurisdictions.
There have been a number of attempts to design safer and less costly flasher units. U.S. Pat. No. 5,408,754, for example, discloses a "motion activated illuminating footwear and light module therefor" in which the sole "improvement" over the prior art involves the replacement of mercury or pressure sensitive switches by a less expensive conventional coil spring actuated switch. Although the light module described in this patent achieves cost savings by using a less expensive switch, the switch used is not as sensitive as a mercury switch, and the system described in the patent still requires a relatively expensive lithium battery, resulting in a light module having substantially decreased performance with minimal overall cost savings.
One reason that the conventional motion sensitive switch, an example of which is illustrated in FIG. 3-1, is less sensitive to vibrations is that the soldering of the switch's inner spring contact to a printed circuit board results in a relatively small vibration angle for the spring contact. The addition of a plastic weight at the end of the spring to increase the inertia of the contact improves electrical engagement between the spring contact and the conductive casing of the switch, but does not increase the vibration angle. Furthermore, the manner in which the spring is soldered to the circuit board makes it likely that solder will be present on the upper portion of the spring, reducing the elasticity of the spring.
Another disadvantage of this arrangement is that the LEDs in this arrangement have one lead soldered directly to the battery, requiring the legs of the LED to be bent during assembly. This has the disadvantage of making assembly without breaking the leads difficult, and also makes it impossible for the user to replace the battery.
Because footwear illumination arrangements such as the one disclosed in U.S. Pat. No. 5,408,764 tend to use non-replaceable soldered-in battery arrangements, the footwear is discarded with the battery when the battery has reached the end of its useful life. Even if the footwear does not outlast the battery, the battery still must be discarded with the shoe. This is not only disadvantageous in terms of cost, but also dangerous to the environment, a problem which is compounded in the case of soldered battery terminals by the problem that most of the batteries are damaged during assembly as a result of the high solder temperatures required (&gt;500.degree. C.), most batteries having been designed to withstand a temperature of no greater than 50.degree. C. While use of a battery bracket can alleviate the problem of heat damage, the problem of irremoveability remains in conventional designs.
Other footwear illumination arrangements are disclosed in U.S. Pat. Nos. 4,848,009, 4,158,922, and 3,893,247, but these arrangements also have the disadvantage of a relatively high cost power source and less than optimal switching arrangements.